Three-way catalytic converters for motor vehicles are known. Such three-way catalytic converters control the emission of nitrogen oxides (NOx). Such three-way catalytic converters typically use a catalyst material that reduces nitrogen oxides to nitrogen and oxygen in the presence of a reductant gas (H2, CO, or hydrocarbon); oxidizes carbon monoxide to carbon dioxide in the presence of an oxidizing gas: 2CO+O2→2CO2; and oxidizes unburnt hydrocarbons (HC) to carbon dioxide and water in the presence of an oxidizing gas: CxH2x+2+[(3x+1)/2]O2→xCO2+(x+1)H2O.
The above reactions are known to occur most efficiently when a catalytic converter receives exhaust from an engine that is operated within a narrow band of air-to-fuel ratios near stoichiometry, such that the exhaust gas oscillates between slightly rich (excess fuel—reducing) and slightly lean (excess oxygen—oxidizing) conditions. Also, it is known that improved fuel economy occurs when fuel combustion occurs with excess oxygen, as seen in lean burn gasoline or diesel engines. Unfortunately, under lean engine operation, excess oxygen is present and the reduction of NOx is not favored.
Therefore, an improved three-way catalytic material that allows for the reduction of NOx in an oxidizing environment would be desirable. In addition, a process for reducing NOx in an oxidizing environment would also be desirable.